1. Technical Field
The present invention relates to a liquid crystal display apparatus for displaying an image utilizing reflected light.
2. Background Art
In recent years, information terminal devices represented by cell phones become widely used and obtain higher performance simultaneously. A liquid crystal display apparatus is often provided with these information terminal devices. It is important for these information terminal devices to improve visibility of the liquid crystal display apparatus and to reduce power consumption (especially, for battery-powered information terminal devices).
As a backlight, a light source (e.g. an LED, a cathode-ray tube, or the like) is arranged at the back of a transparent or semi-transparent type of liquid crystal display apparatus, thereby improving visibility thereof. A light source having low directivity is generally used in order to radiate back light within a wide area evenly.
FIG. 11 illustrates a configuration of a conventional liquid crystal display apparatus utilizing a backlight. The conventional liquid crystal display apparatus illustrated in FIG. 11 comprises a light source 2 of the backlight at the back of a liquid crystal device 1. Light from the light source 2 penetrates the liquid crystal device 1, reaches a view area 3, and is visible within a wide area.
In the conventional liquid crystal display apparatus as shown in FIG. 11, it is necessary to use the light source 2 having sufficient luminance in order to make a display content favorably viewable within the wide view area. As a result, the wider the view area 3 is, (in other words, the greater a visual angle of the liquid crystal display apparatus is,) the more power consumption of the light source 2 becomes.
Document 1 (Published Japanese patent application no. 2003-131230) discloses a configuration of a liquid crystal display apparatus, including: a light source means; means for increasing luminance; a liquid crystal display device; a first optical element; and a second optical element. In the liquid crystal display apparatus disclosed in Document 1, the first optical element is provided with a plurality of convex lens corresponding to a plurality of pixels of the liquid crystal display device, and the second optical element is provided with a plurality of concave lens for cancelling refractivity of the first optical element. When used within a narrow visual angle, the first and second optical elements are in close contact with each other, thereby cancelling the refractivity. When used within a wide visual angle, the first and second optical elements are kept at some distance from each other, thereby making use of the refractivity. Document 1 says that the configuration of the liquid crystal display device disclosed therein enables to control the visual angle. The liquid crystal display device disclosed in Document 1, however, does not possess mechanism for dynamically changing setting of a range and a direction of the visual angle. The setting is fixed.
Document 2 (Published Japanese patent application no. 2001-311946) discloses technology of controlling a visual angle of a reflective liquid crystal device. FIG. 12 illustrates a configuration of a conventional reflective liquid crystal device operable to control the visual angle. The reflective liquid crystal device illustrated in FIG. 12 is provided with reflecting plates 4a, 4b, and 4c, each of which reflects extraneous light 5 toward the back of a liquid crystal device 1. The reflecting plates 4a, 4b, and 4c are composed of small mirrors provided for every pixel. The small mirrors are equipped with a reflection angle adjuster and are operable to adjust the angles. The angles of the reflecting plates 4a, 4b, and 4c are adjusted so that reflected light radiates toward a user through this reflective liquid crystal device. Since extraneous light is used as light for display, the reflective liquid crystal device disclosed in Document 2 contributes to low power consumption, however, it is difficult to obtain sufficient luminance within a whole view area. Especially, there is a problem that the device does not work well in a dark place where extraneous light is poor.
As discussed above, it is difficult for conventional liquid crystal display apparatuses to simultaneously realize securing favorable visibility and reducing power consumption.    [Document 1] Published Japanese patent application no. 2003-131230    [Document 2] Published Japanese patent application no. 2001-311946